What are the four modes of evolution?

Mutation

• Provides new alleles, and therefore are the ultimate source of variation.

• Is an change in the DNA nucleotide sequence of an allele.

• May not immediately affect the phenotype.

• Can be beneficial, neutral, or harmful

Examples of Mutation

Migration

• Enables gene flow: the movement of genes from one population into another.

• Continued gene flow decreases diversity among populations, causing gene pools to become similar

Example of Migration

• Some beetles with brown genes immigrated from another population, or some beetles carrying green genes emigrated.

Natural Selection

• Is the process that results in adaptation of a population to the environment.

• Natural selection requires:– variation             – inheritance             – differential adaptedness– differential reproduction

Natural Selection

• Natural Selection enables beneficial mutations to be passed on to the next generation.

• These beneficial mutations are called

ADAPTATIONS

Example of Natural Selection

• Beetles with brown genes escaped predation and survived to reproduce more frequently than beetles with green genes, so that more brown genes got into the next generation

Genetic Drift

• In each generation, some individuals may, just by chance, leave behind a few more descendents (and genes, of course!) than other individuals. The genes of the next generation will be the genes of the “lucky” individuals, not necessarily the healthier or “better” individuals.